clxxxvii 



atmosphere. I own a horse now that will drink from 25 to 30 gallons of 

 water everv day during warm weather. As with man, so with our domes- 

 tic animals, one will drink more in a given length of time than another. 

 In arriving at the total amount consumed, I estimated thus for 24 hours : 



1.000,000,000 horses, 12 galls, each, - - 12,000,000.000 



2,000,000,000 cattle, 25 " " - - 50.000,000,000 



2,000,000,000 sheep, I " " - - 2,000,000,000 



3,000,000,000 hogs, 2 " " - - 6,000,000,000 



Total, - - 70,000,000,000 



This, I think, will be found to be as nearly correct as it is possible to 

 make it. 



One word with reference to the horse. Carpenter says : "Of the -water 

 taken into alimentary canal or contained within the body, nearly two-thirds 

 passes off with the fteces : and of that which is absorbed, little more than 

 one-seventh passes into the urine, the remainder being exhaled from the 

 lungs and skin." Now I found after repeated measurement that the quan- 

 tity of urine passed by a horse in 24 hours would average one gallon and a 

 half; taking even this as a basis for estimating the probable amount of 

 water consumed during the day, and it will be found that my calculation 

 for the horse does not exceed the true amount. 



Thanking you for your courtesy in calling my attention to this subject, 

 and with my best wishes for your prosperity and happiness, I remain 



Very truly yours, &c., 



AMOS SAWYER. 



Dr. Theodore Fay presented a hydrograph of the Missisippi 

 River, at the foot of Market street, showing the rise and fall of 

 the river from 1844 to 1875. The highest point attained by the 

 river the present season was on the 8th of August, when the wa- 

 ter was five feet below the city directrix. The highest water was 

 in 1844, the lowest in 1863. The map is on vellum, and four by 

 five feet in size. A vote of thanks was tendered to the donor. 



Prof. F. E. Nipher made some striking experiments with col- 

 ored glass, the substance of which was published in the "Notes" 

 in Nature for Oct. 7, 1875. It is well-known that if the eye be 

 forced to look steadily at a certain color — as, for instance, red — 

 the sensation of red is gradually enfeebled. If now the eye be 

 fixed on a sheet of white paper, the red which goes to make up 

 the white is enfeebled, and the remaining colors impress the eye 

 with the sensation of green. What is true of red and green is of 

 course true of any other complementaiy color. — A much more 

 striking effect is produced if some white and brilliantly illumin- 



